Add JSP snippets - #66

After using this for myself for some time I discovered a usability problem with the JSTL Tag Snippets:
For example

<c:if<tab>

results in

<c:<c:if test="${true}">
</c:if>

because if is a snippet prefix.
I don't know what would be a good alternative... Maybe <c:if instead of if, but that's pretty verbose.

Or is it possible to use a regex like (?:^|[^:])if as prefix?

I figured it would be nice if "tag snippets" would only work outside of tags. So that this:

<div out[tab]>
</div>

wouldn't result in this:

<div <c:out value="${}"/>>
</div>

Hmm. c:if should definitely take priority over just if. I wonder where that matching occurs.

@50Wliu I've done some research on that <c:if vs if problem:
The snippets package does -- probably for performance reasons -- some complicated stuff, but basically it just checks if the text behind the cursor is equal to the prefix of a snippet in scope and if that's the case, it replaces the prefix with the snippet text.

Now I could do two things:

• Add a second version of each "tag snippets" whose prefix starts with <c:
• Add a second version of each "tag snippets" with out any prefix. That's what the language-html package has done. This will remove the snippets inside tags.

I prefer the first method, but I don't like that this means I have to duplicate all the code.

I fixed this problem in the last commit. It's not perfect because it adds some redundancy, but I think it's the best we can get. Correct me if I'm wrong.